"Today, we are making an act of defiance and of responsibility: defiance because we'll prove that the government has lost its majority, and responsibility because we'll let the budget pass," said Dario Franceschini of the Democratic Party, the biggest opposition group.

The budget bill, including a range of austerity measures demanded by European leaders, needed to pass "not for the good of the government, but for the good of the country," said Benedetto Della Vedova of the Future and Freedom party, a conservative break-away group from Berlusconi's governing People of Freedom party.

In a bid to change the minds of last-minute defectors, Fabrizio Cicchito, a Berlusconi's party spokesman, had said: "We have done everything that Europe has asked us to do. Let us be reminded that it is not the markets that elect governments. Let us do our part like we have done over the last couple of years."

The vote comes after weeks of intrigue and rumours of defections in Rome. A painful blow to Berlusconi came when his long-time ally and coalition partner, Umberto Bossi of the Northern League, earlier on Tuesday urged him to step down.

What happens next is unclear. The president of the republic, Giorgio Napolitano, has the power to dissolve parliament, but it remains to be seen whether he will do so.

Berlusconi has said he would await today's vote and decide later whether to step down or not. If so, he has said he would push for new elections instead of a government of national unity.

He might decide to stay on and push for a vote of confidence in the Senate however, where he still holds a comfortable majority. Such a move would inevitably push the opposition in the lower house to call for a vote of no confidence there as well. But the maneuvering would allow Berlusconi some time to try and regain the support of defectors.

For his part, opposition leader Pier Luigi Bersani in his closing remarks on Tuesday said Berlusconi's reluctanc to let go the reins is doing damage to the country's fragile financial situation.

"Everybody knows that Italy runs the risk in the coming days of losing access to the financial markets. I call on Berlusconi to resign and to entrust the head of state with the task of searching for a new government. If he does not, the opposition will resort to other measures," he said.

Following a humiliating rout in parliament on Tuesday, Italian Prime Minister Silvio Berlusconi has said he will resign immediately after a package of austerity measures is approved - a development expected in the coming weeks.

The interest rate on Italian 10-year government bonds breached seven percent on Wednesday, shattering the psychological bail-out ‘ceiling’. Greece, Portugal and Ireland all had to seek multi-billion-euro bail-outs when their 10-year bonds exceeded this threshold.

Opinion

Defining what constitutes 'rule of law' violations may be more difficult than the EU Commission proposes, as it tries to link cohesion funds in east Europe to judicial independence. A key question will be who is to 'judge' those judges?